Her assistant said Reagan died at her home in Los Angeles of congestive heart failure.

She will be buried next to her husband at the Ronald Reagan Presidential Library in Simi Valley, California, the library said in a statement.

Born Anne Frances Robbins, she was a Hollywood actress before marrying prominent actor Ronald Reagan in 1952.

The marriage, which lasted 52 years until his death in 2004, was once described as the greatest love affair in the history of the American presidency.

Reagan became one of the most influential first ladies in U.S. history during her Republican husband's presidency from 1981 to 1989.

She was Reagan's closest adviser and fierce protector on his journey from actor to governor of California to president of the United States, and later endured his nearly decade-long battle with Alzheimer's disease.